i Transcoding Transport Stream MPEG2 __________________________________________________________ A thesis Presented to the Faculty of Graduate School University of Missouri – Columbia __________________________________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science __________________________________________________________ by Shashi R. Shilarnav Dr. Gordon K. Springer, Thesis Supervisor May 2007 ii The undersigned appointed by the Dean of the Graduate School, have examined the thesis entitled TRANSCODING TRANSPORT STREAM MPEG2 Presented by Shashi R. Shilarnav A candidate for the degree of Master of Science And hereby certify in their opinion it is worthy of acceptance. ____________________ Dr. Gordon K. Springer ____________________ Dr. K. Palaniappan ____________________ Dr. William H. Miller ii Acknowledgements I would like express my sincere gratitude to all the people who have helped m e throughout m y M aster‟s degree. I am very m uch thankful tor. DGordon Springer for his guidance and support which helped me complete my research and graduate studies. His patience and persistence not only led me into an exciting field of computer programming, but also educates me with his philosophy of science and life. I would like to thank Dr. William Miller and the Nuclear Science and Engineering Institute for the support throughout my graduate studies. I also express my gratitude to Dr. K Palaniappan for serving on my Master of Science program committee. ii iii TRANSCODING TRANSPORT STREAM MPEG2 Shashi R. Shilarnav Dr. Gordon K. Springer, Thesis Supervisor ABSTRACT Video conferencing provides students with the opportunity to remotely attend classes and participate in a 2-way communication with the teacher. Nuclear Science and Engineering Institute at the University of Missouri – Columbia has been using VBrick to facilitate distant learning through video conferencing. Multicast protocol is used to deliver DVD quality MPEG2 video to audience during class room sessions. This thesis looks into the possibilities of delivering these lectures live to audience that do not have connectivity to Internet2 and the problem with transcoding transport stream MPEG2 (generated by the VBrick) to lower bit-rate is addressed. A framework to transcode transport stream MPEG2 into other formats like Windows Media Video, H.264 and Real Video is proposed. Existing tools like Windows Media Encoder and Real Producer is used in this framework. A GUI application to facilitate the use of this framework is designed using Qt. In addition the comparison of the transcoded video is made by measuring its Peak Signal to Noise Ratio and the compression statistics. iii iv Table of Contents Acknowledgements…………………...……………………………………………………….…ii Abstract..................................................................................................................................…...iii List of Figures………………………………………………………………………...….......…vii List of Tables………………………………………………………………………………...…..ix 1. Introduction…...………………………………………………………………..1 1.1 Foreword…… ……… ……… ……… …… ………… ……… ……… …...1 1.2 Thesis contribution… … ...… … … … … … … … ….… … … … … .… ...2 … … 1.3 Thesis organization… … … ...… … … … … … … … … … … … … … .… … ...3 2. Theoretical framework…………………...……………………….…………..4 2.1 Fundamental concepts of video and audio............................................4 2.1.1 Video… … … … … … … … … … … … … … … ...… … … … … … … … … … … … 4 2.1.2 Audio… … … … … … … … … … … … … … … ...… … … … … … … … … … … … 5 2.2 Compression… … … … ..… … … … … … … … … … … … … … … … … … ..6 2.2.1 Lossless and lossy co m pression… … … … … ..… … … … … … … … … … … ..7 2.2.2 Motion compensation…… …………………………………………………9 2.2.3 Discrete wavelet transform … …..... …………………………………………9 2.3 Video compression standards… … … … … … … … … … … … … … … ...10 2.3.1 H.261, H.263, H.264… … … … … … …………………………….10 … … … … 2.3.2 MPEG… … … … … … … … … … … … … … … ....… … … … … … … … … … … 10 2.4 Principles of MPEG2.............................................................................12 2.4.1 Video sequence.............................................................................................13 2.4.2 Frames...........................................................................................................14 2.4.3 Slices.............................................................................................................15 2.4.4 Macro-blocks and blocks..............................................................................16 2.4.5 Fields.............................................................................................................18 2.5 Program stream and transport stream MPEG2....................................18 2.5.1 MPEG2 program stream..............................................................................19 2.5.2 MPEG2 transport stream.............................................................................19 iv v 3. Video streaming protocols and standards.......................................................25 3.1 VBrick....................................................................................................25 3.2 Protocols for video streaming over Internet.....................................27 3.2.1 Media delivery protocols............................................................................27 3.2.2 Unicast.........................................................................................................28 3.2.3 Multicast.....................................................................................................29 3.3 Media control protocols .....................................................................31 3.3.1 Real time streaming protocol....................................................................31 3.3.2 Microsoft media server protocol ................................................................32 3.3.3 Hypertext transfer protocol........................................................................33 3.4 Protocol rollover.....................................................................................33 3.5 Streaming vs. downloading......................................................................34 3.5.1 Downloading................................................................................................35 3.5.2 Streaming.....................................................................................................35 4. Transcoding video streams..............................................................................36 4.1 Types of video transcoding: homogeneous and heterogeneous.............37 4.1.1 Homogeneous transcoding..........................................................................38 4.1.2 Heterogeneous transcoding.........................................................................38 4.2 Transcoding VBrick transport stream MPEG2......................................40 4.2.1 Windows media server.................................................................................45 4.2.2 Real helix server.........................................................................................52 4.2.3 VideoLan client............................................................................................56 4.3 Quality of transcoded stream..................................................................57 5. Results and conclusions....................................................................................60 5.1 Results.....................................................................................................61 5.1.1 Compression statistics..................................................................................61 5.1.2 Quality of transcoded video..........................................................................62 5.1.3 Delay.............................................................................................................64 5.2 Conclusions.............................................................................................68 5.3 Future work............................................................................................69 v vi References...............................................................................................................71 Appendix A Source code for wp2wmv GUI application........................................74 Appendix B Usage of VideoLan client...................................................................83 vi vii List of Figures Figure 2.1 Discrete wavelet transform.............................................................................................9 Figure 2.2 Comparison of the resolution in various standards......................................................11 Figure 2.3 MPEG2 video structure...............................................................................................13 Figure 2.4 MPEG stream as a Group of Pictures...........................................................................14 Figure 2.5 Skipped macro-blocks in a P-frame............................................................................17 Figure 2.6 Skipped macro-blocks in a B-frame.............................................................................17 Figure 2.7 Overview of MPEG2 transport stream........................................................................20 Figure 2.8 Transport stream MPEG2 packets...............................................................................21 Figure